环境因素对芸苔链格孢生长发育的影响

EFFECT OF ENVIRONMENTAL FACTORS ON DEVELOPMENT OF ALTERNARIA BRASSICAE

研究结果表明,芸苔链格孢(Alternaria brassicae)在0—35℃下均可萌发,最适温度15—20℃。菌丝在0—30℃下均能生长,最适温度20—25℃;孢子及菌丝的致死温度为50℃,10分钟。该菌对湿度要求较严格,相对湿度在90％以上时孢子才能萌发,最适相对湿度为98％;病菌在相对湿度达93％时可以侵染,98％以上最适。脱落后孢子曝露在室内(相对湿度约63％)经1小时萌发率下降32.4％,4小时下降80％。耐旱能力较差。一般情况下紫外光能促进该菌产孢,但是对某些菌系的促进作用不明显。过长的紫外光照射对该菌产孢不利,照射160分钟孢子萌发率下降近80％。麦芽糖、蔗糖为该菌的最佳碳源;硝态氮、有机氮是该菌的良好氮源。pH值为4—6时有利于分生孢子萌发,强酸、强碱对分生孢子萌发有抑制作用。

Results indicated that spores of Alternaria brassicae could germinateat a temperature ranging from 0 to 35℃ with an optimum of 15 to20℃.The mycelium of the fungus grew between a temperature range of0 to 30℃ and the optimum temperature was 20 to 25℃.Both sporesand mycelium lost viability completely within 10 minutes when exposedto a temperature of 50℃ Spore germinated only when the relative hu-midity was above 90%,with 96% as the optimum for both germinationand infection.A minimum of 93% relative humidity was required forsuccessful infection.The germination of spores that were isolated fromnutrient source was decreased by 32.4% after 1 hour and 80% after 4hours under 65% relative humidity at room temperature.Ultravioletlight (UV) generally promoted sporulation.However,sporulation ofsome strains did not respond significantly when exposed to UV-light.prolonged treatment of spores with UV-light had a negative effect ongermination.The germination of spores was reduced by 80% when ex-posed to UV-light for 160 minutes.Maltose,sucrose,nitrate nitrogen andorganic nitrogen were the best sources of carbon and nitrogen,respec-tively,for growth of the fungus.A pH range of 4 to 6 favored sporegermination,but germination was inhibited by high and low pH.